Evolutionism is a term used (often derogatorily) to denote the theory of evolution. Its exact meaning has changed over time as the study of evolution has progressed. In the 19th century, it was used to describe the belief that organisms deliberately improved themselves through progressive inherited change (orthogenesis). The teleological belief went on to include cultural evolution and social evolution. In the 1970s, the term "Neo-Evolutionism" was used to describe the idea that "human beings sought to preserve a familiar style of life unless change was forced on them by factors that were beyond their control."

The term is most often used by creationists to describe adherence to the scientific consensus on evolution as equivalent to a secular religion. The term is very seldom used within the scientific community, since the scientific position on evolution is accepted by the overwhelming majority of scientists. Because evolutionary biology is the default scientific position, it is assumed that "scientists" or "biologists" are "evolutionists" unless specifically noted otherwise. In the creation–evolution controversy, creationists often call those who accept the validity of the modern evolutionary synthesis "evolutionists" and the theory itself "evolutionism".